The numbers of alleles, allele frequencies, and allele frequency differences among Native American tribes will be ascertained for the short tandem repeat (STR) loci that are being employed in our linkage analyses. Approximately 30 individuals from each of 20 tribes collected primarily at the Albuquerque Indian Hospital will be analyzed. Tests for allele frequency differences between tribal groupings based on cultural and linguistic affinities will be performed. This information is important to genetic linkage and disease association studies on Native Americans because poor estimates of allele frequencies can result in false evidence for linkage, and allelic heterogeneity among groups can create spurious associations with disease.